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    <script>
        // 需求：求数组[2,6,1,7,4]里面所有元素的和以及平均值
        let arr = [2, 6, 1, 7, 4]
        let sum = 0
        for (let i = 0; i < arr.length; i++) {
            sum += arr[i]
        }
        console.log(`数组的和的结果是：${sum}`)
        console.log(`数组的平均值的结果是：${sum / arr.length}`)
    </script>
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